This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Rotavirus is a major pathogen of infantile gastroenteritis. It is an icosahedral virus, 1000 [unreadable] in diameter, with a complex architecture consisting of three concentric capsid layers enclosing 11 dsRNA segments. Over several years we have been trying to determine the structure of various forms of this medically important virus. We are presently using the NCMI facility to carry out high-resolution structural analysis of transcriptionally competent, transcriptionally incompetent and transcriptionally active forms of rotavirus particles, to understand molecular mechanisms underlying the fascinating process of endogenous transcription in these viruses. In addition, we also study various molecular components of rotavirus. Rotavirus viroplasms form by expression of nonstructural proteins NSP2 and NSP5. These viroplasms formed during viral infection provide excusive sites for genome replication/packaging and capsid assembly. Little is known about the structural basis of how these processes are coordinated within these viral factories. Norwalk virus is a prototype norovirus, which are causative agents of acute epidemic gastroenteritis.